(1) Field of the Invention
The invention relates to a subterranean well tool incorporating a slip assembly for anchoring the well tool along an inner wall of a conduit against movements in at least one direction. A subterranean well tool includes an elastomeric seal and the slip assembly.
(2) Description of the Prior Art
Subterranean well tools, such as packers, bridge plugs and the like, often are introduced or carried into a subterranean oil or gas well on a conduit, such as wire line, electric line, continuous coiled tubing, threaded work string, or the like, for engagement at a pre-selected position within the well along another conduit having an inner smooth wall, such as casing. It is desired that the well tool be set and anchored into position along the smooth wall of the desired conduit such that movements in various directions such as upwardly, downwardly, and/or rotationally, are resisted, and, in fact, prevented. Such movements may occur as a result of a number of causes, such as pressure differentials across the tool, temperature variances, tubing or other conduit manipulation subsequent to setting for activation of other tools in the well, and the like. Accordingly, devices commonly referred to as xe2x80x9cslipsxe2x80x9d or xe2x80x9cslip assembliesxe2x80x9d have been utilized for the anchoring function.
Typically, such slip assemblies are manufactured of a frangible cast iron which is intended to fracture into segments upon outward expansion to the set position. The fracture event is nearly xe2x80x9cexplosivexe2x80x9d and the slip segments can jump off and away from the plug or packer housing and even fall down hole. Such slips are usually driven radially outwardly to the set position by means of a circular cone-type component which is driven by an activating mandrel against the inner wall of the slip elements to separate them such that teeth defined around the outer surface of the separated slip members may be driven into the wall of the conduit. Fragmenting slip segments can break up non-uniformly and orient in a skewed alignment or non-uniform circumferential distribution on the wedging cone, resulting in the axis of the plug or packer tool to be non-concentric and non-parallel with the longitudinal center line of the casing or other tubular. This result could adversely effect the anchoring and sealing performance of the packer or other tool incorporating the slip assembly. In other words, in many instances, the individual slip elements may not expand outwardly in one radial plane such that they are in continuous planer alignment during the expansion movements. This may result in one slip portion being set higher or lower than other slip portions and could result in a breaking or other failure, such as metallic fatigue, in the slip component, resulting in skewing and misalignment of the packer or bridge plug in the well.
The present invention is directed to the problems associated with the prior art set forth above.
In one aspect, the present invention provides a slip assembly for anchoring a subterranean well tool, such as a packer, bridge plug, or the like, along the inner wall of a conduit, such as casing, against movements in at least one direction, or, preferably, any direction. In particular, the slip assembly is particularly useful when the well tool is to be designed for applications requiring high expansion ratios between run-in and set positions. The slip assembly comprises a series of radially aligned slip means, which may be a series of breakable slip elements or, alternatively, may be provided in any configuration known to those skilled in the art. The slip means are moveable from a contracted position to an expanded position when it is desired to anchor the well tool within the well along the inner wall of the conduit. Means such as a flat wrapping of metal, a spring or the like, are provided for applying a very rigid, stiff continuous, radial inwardly urging bias against the slip means, whereby the slip means move in a substantially uniform plane of expansion parallel with the longitudinal center line of the tubular conduit upon which the device is to be anchored during movements to said expanded position.
In another aspect, the invention defines a slip assembly in which a receiving profile including first and second shoulders are defined on the slip means. Means, such as a continuous length or belt of metallic material, such as a band of flat stainless steel wire, is wrapped within the profile with each layer abutting the shoulders, thereby applying a stiff continuous inwardly urging circumferential bias against the slip means during movements to the expanded position. Means, such as a length of thin bailing wire, may, in turn, be wrapped around the layers of the metal belt for reducing the bias resulting from the wrapping configuration of the belt around the slips as the slips are moved toward the expanded position while also resisting unwrapping of the belt means. In another aspect, the invention provides a subterranean well tool for setting along the inner wall of the first conduit and against movements in at least one direction. Means, such as threads, or other typical connection are provided for securing the tool to a second conduit, such as continuous coil tubing, for introducing and carrying the tool within the well to a preselected position. An elastomer providing a packer component is moveable into sealing relationship on the inner wall during the setting of the subterranean well tool. A slip assembly is provided for anchoring the well tool along the inner wall and against movements in at least one direction. The slip assembly is as previously described.
In yet another aspect, the invention also provides a back-up, or secondary, seal system for incorporation into a well tool having a primary elastomeric seal component and may be used with or without the slip assembly described herein.